Work machines, such as wheel loaders, off-highway trucks and other heavy construction and mining machines, are used to perform many tasks. To effectively perform these tasks, a work machine requires a power source such as a diesel engine, a gasoline engine, a natural gas engine, a turbine engine or any other type of power source that provides the power required to complete these tasks. Such work machines typically include a drive system that may include one or more drive motors for powering traction devices to propel the work machine.
Some work machines include a drive system with multiple, independent drive motors. Typically, each drive motor of such a drive system powers a different subset of the traction devices of the work machine. For example, some work machines include four drive motors, each of which independently powers one of four traction devices of the work machine. In some circumstances, a subset of the drive motors of such a work machine bear most or the entire burden of propelling the work machine. When traction is unevenly distributed between the traction devices, those drive motors connected to traction devices with good traction have to provide most of the power to propel the work machine.
At least one multi-motor drive system has been constructed with drive motors that supplement one another in powering the traction devices of the work machine. For example, U.S. patent application No. 2004/0121871 (“the '871 application”) by Thompson, published on Jun. 28, 2004, shows a multi-motor drive system with three propulsion motors, each of which is operatively connected to and drives a wheel of the work machine. The '871 application shows three pairs of wheels spaced along the length of the work machine. One drive motor is connected to the right, front wheel, another drive motor is connected to the right, rear wheel, and another drive motor is connected to the left, rear wheel. One transmission connects the three wheels and the two drive motors on the right side of the work machine and another transmission connects the three wheels and the one drive motor on the left side of the work machine. A single cross-shaft with a differential unit connects the transmissions on the right and left of the work machine. Thus, power can transfer from each drive motor to various wheels of the work machine. A steer motor connected to the differential unit controls the speed differential between the wheels on the right and left sides of the work machine.
Although the design of the drive system of the '871 application allows sharing of drive loads between the drive motors, the design includes disadvantages. The single cross-shaft of the drive system necessitates the use of cumbersome transmission units extending along the length of the left and right sides of the work machine for transferring power from the cross shaft to the front and rear wheels. This configuration is poorly adapted for use in many work machine applications. The use of a single differential dictates that all of the wheels on the right side of the work machine rotate at the same speed and, likewise, that all of the wheels on the left side of the work machine rotate at the same speed. Additionally, the design requires the use of a steer motor to induce turning of the work machine, which increases the cost of the drive system and complicates the process of controlling the motors of the drive system.
The drive system of the present disclosure solves one or more of the problems set forth above.